Hi Favour Ezema,
where a couple hold joint loan accounts, both account holders are liable both in their own right and jointly. This means that the bank is entitled to recover the debt from both of you jointly and/or from each of you individually if there is any default.
Therefore even if you agree between yourselves that your wife is to take responsibility for the joint debt does not change the right of the bank to require either or both of you to pay the debt. The bank has to consent to the re-allocation of liability for the loan before it will be bound by any such agreement. However, as Rod said, the bank may be compelled to re-allocate liability where a Court has made an order binding on a third party pursuant to family law legislation. Therefore one option is to get the court to reallocate your assets.
Another option may be for your wife to take out another loan by herself to payout the joint loan on the car if possible.
Finally, you may be able to discuss it with the bank and come to an agreement whereby you are removed from the loan and your wife is the sole borrower on it, if she now satisfies financial and credit requirements.